Forgive me if I'm saying anything that's been stated here. The Lord has taught me a lot in this area and I pray that He uses my experiences to help you.
Matthew 5:23-24 states
Therefore if you bring your gift to the altar, and there remember that your brother has ought against you; Leave there your gift before the altar, and go your way; first be reconciled to your brother, and then come and offer your gift.
as a few people said already, by you holding onto your anger towards them, it is and in time will be breeding sin. It can also hinder your prayers. It's one thing to be angry at them while you know no better of the importance of forgiveness. But you know now and from this point on to choose to live in anger towards them instead of desiring or seeking God's love for them would be deliberately choosing the enemy.
On another note and viewpoint. Forgiveness can be confusing once you're asked to do it. And only Jesus can help you with this since he is the author of forgiveness and your salvation is a direct result of his forgiveness of you. So much so, that he was willing to shed his pure blood so that you or your parents don't have to shed theirs. The world teaches us that this is a pay back world. That's the way things operate and the way you gain anything is to hold it to your self and don't give it to anybody needy who should have known better. Jesus and his principals are different. If you want to gain your wealth and life in Christ, you need to at least be willing at His call to lose your earthly possessions and even teachings. Just loving him and asking forgiveness for your anger, and asking his heart and viewpoint on the situation should plant the desire to start forgiving them. Start praying for them. This will also be a way that you would be choosing Jesus over dwelling in your anger.
My father died when I was 3. Growing up, my mother has been very cruel to me. She's called me worthless, trash, dog. And there were a lot of other problems/issues with her I was still needing healing from after coming to Christ. Until a year ago I never understood forgiveness, I knew God was calling me to forgive my mother but I had no idea how. I prayed for the ability to forgive her. There were so many old buttons from my mom that even strangers could absent mindedly push while dealing with me which would lead to me being in pain and reminded that I was damaged. I would just tell myself that my mom didn't' know any better because she didn't know God and take the brunt of everything, and that's how I mentally "forgave." God showed me that forgiving is no longer putting the responsibility of not hurting you on the other person but not because they didn't know better. It's also no longer waiting for their heart to change and suddenly apologize and love you again, but rather put the responsibility of perfect love on God. All in all, when anything else is given the responsibility of perfect love and given the power of determining your happiness, they become an Idol. Only God is fit for that platform.
I started praying that God would work in my heart. I wasn't really angry at this point. But I was still in a hopeful waiting state to finally have the perfect loving motherly mom. I was allowing her to be in charge of my happiness and looking to her for love, so the wounds remained because she was unloving. I needed God to heal them. I quit contacting my mom or answering her phone calls for a while just so that I wouldn't be hurt and go back in the cycle with her. Then I got prayer from a specific healing ministry. Afterwards I felt like that area and subject of my life was a blank sheet of paper. Nothing painful, nothing hopeful in my mom. All my hope and love was in God and it felt sooo good to be free from that burden. The next day my mom called wanting to get together and since then she's been a completely different person. I believe in the miracles God can work through prayer. But I always prayed for this healing and it had never come before. God showed me that I had to let go of my mom who I'd made into an idol that I couldn't even forgive before I could be blessed by his love and healing in that place.
I really pray this helps you in tremendous ways.
God Bless you and if THIS is what God has given you straight out of salvation, I can't imagine the wondrous plans for you and wisdom He has to teach you through this.
The Lord just gave me this for you:
Luke 4:16-21
New King James Version (NKJV)
Jesus Rejected at Nazareth
16 So He came to Nazareth, where He had been brought up. And as His custom was, He went into the synagogue on the Sabbath day, and stood up to read. 17 And He was handed the book of the prophet Isaiah. And when He had opened the book, He found the place where it was written:
18 “ The Spirit of the LORD is upon Me,
Because He has anointed Me
To preach the gospel to the poor;
He has sent Me to heal the brokenhearted,[a]
To proclaim liberty to the captives
And recovery of sight to the blind,
To set at liberty those who are oppressed;
19 To proclaim the acceptable year of the LORD.”
20 Then He closed the book, and gave it back to the attendant and sat down. And the eyes of all who were in the synagogue were fixed on Him. 21 And He began to say to them, “Today this Scripture is fulfilled in your hearing.”
Imagine how Jesus must have felt going back to his home town. He grew up with him. They probably had misconcieved notions about him and thought that they wouldn't need to hear whatever was coming out of his mouth. AND he practically says he's the savior to them. Jesus is going to use you in amazing ways with your family, but first you need to see his power and His love before their circumstances and "impending" death. Jesus wants you to see your family the way he lovingly desires their hearts and with his eyes and not JUST because they may or may not die soon, but because it's a blessing to be able to love one another through our father's eyes and grow with HIM.
There are so many possibilities. I pray that your visit home will go well. Lean on God for strength 
