Well certainly Lazarus was a disciple and indeed was loved by Jesus, for Jesus certainly revived him when everyone else thought he was dead. Lazarus though is not the beloved disciple. The beloved disciple, or the disciple whom Jesus loved, is found only in the Gospel of John, and at the very end John identifies this as himself. I think it is just John's peculiar way of writing and telling his story.
John 21:20-24
20 Then Peter, turning about, seeth the disciple whom Jesus loved following; which also leaned on his breast at supper, and said, Lord, which is he that betrayeth thee?
21 Peter seeing him saith to Jesus, Lord, and what shall this man do?
22 Jesus saith unto him, If I will that he tarry till I come, what is that to thee? follow thou me.
23 Then went this saying abroad among the brethren, that that disciple should not die: yet Jesus said not unto him, He shall not die; but, If I will that he tarry till I come, what is that to thee?
24 This is the disciple which testifieth of these things, and wrote these things: and we know that his testimony is true.