Could my former friend's girlfriend be jealous?

I had been friends with a guy for a few years and once he started dating his current girlfriend he cut all his friends from his life, most of whom call him and receive no response, the few who do say he isn't the same jovial person. A while back I decided to do a cleaning spree on my FB friends list and low and behold he's gone. I thought it was weird and couldn't find him by looking up his name, soon enough I asked a mutual friend and she said no he still has his page. A month later I see one of his kids (who happens to be my younger brother's friends) and it seems his troubles and possibly my being blocked on his dad's FB precipitated by giving a birthday gift to his sister. I never dated my friend and I'm close to two of his kids. Later on as is my usual custom, I tried to send him a happy birthday text (iPhone messenger) it's going through the whole sending process for most of the day and finally towards nighttime changes from blue to green. I'm kind of daunted for a moment, but realized 1 she has issues and 2 she doesn't trust him. I'm one of those friends who is happy for my friends finding good people, yet I find certain relationships toxic. My friend was the joyful, open, confident, and kind type; yet he has disappeared and been replaced by a quiet, brooding person.
I've been in toxic relationships before and I keep thinking he's in one, but at the same time I keep hoping he's not. I just remember my own experiences about being cutoff from friends until my breakups.

I had been friends with a guy for a few years and once he started dating his current girlfriend he cut all his friends from his life, most of whom call him and receive no response, the few who do say he isn't the same jovial person. A while back I decided to do a cleaning spree on my FB friends list and low and behold he's gone. I thought it was weird and couldn't find him by looking up his name, soon enough I asked a mutual friend and she said no he still has his page. A month later I see one of his kids (who happens to be my younger brother's friends) and it seems his troubles and possibly my being blocked on his dad's FB precipitated by giving a birthday gift to his sister. I never dated my friend and I'm close to two of his kids. Later on as is my usual custom, I tried to send him a happy birthday text (iPhone messenger) it's going through the whole sending

It's "lo" and behold, not "low". Also, why did you post the same thing twice, once anonymously and once using your name?

Anyone who demands their partner give up friends is usually jealous and insecure (and this is a form of controlling emotional abuse as well). The shocking thing here is that this person is apparently also a parent. These are the kinds of abuses we usually learn not to tolerate by the time we're adults. It's pretty messed up.