IRMAC, He's having a moment of sanity. A lot of them will do this around a holiday because they do remember what it use to be like as a family unit. He could very well have been thinking of the great times he had w/you and your family and opted to text you to test the waters to see if you will return the message. Some do it to just remind us that they are still out there, not thinking how it hurts and reminds us of their absence. Some, for selfish reasons, hope that we will be friendly to them so that it will appease their guilt for what they've done....others, well...they aren't really thinking at all.
I personally would not read too much into his behavior. Treat him just as you would a friend and nothing more. Time will reveal to you what is going on w/him.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
