Children are With My Ex-Inlaws

My question involves a child custody case from the State of: Texas and Virginia

When my ex-husband and I divorced, we agreed that since he had stable employment and residence, our two kids would stay with him. He was the custodial parent on the decree but it was joint custody. Shortly after our divorced was finalized, the visitations were going good until he asked for the kids to stay with his parents (Virginia) the first half of summer in 2009. I agreed with the understanding that they would spend the second half of the summer with me. The kids never came back. My ex-husband got caught up in alcoholism and drugs, lost his job/house/everything. I had moved back to Texas that same first half of the summer with my now husband and was never able to communicate with my ex after his downward spiral. I never gave up any rights to my children and since, I have sent letters, left messages and made multiple contact efforts to my ex-inlaws begging for communication with my kids. A former girlfriend of my ex said that he was going to give up his rights to them to his parents. I am in complete disarray with my kids and want desperately to get them back. Where do I start???

This may seem like a silly question - but why haven't you driven up to retrieve the children before now?

You left the children with your former in-laws about four years ago. Have they ever gone to court to get any form of legal custody / guardianship?