Another story/rant from my "blended" family circus.
I have a 22 year old SS which whom I never had issues and whom I always liked. Our shared child is almost 5.
Anyhow, when SS was 15-16, he used to be very caring with our then 7-8 year old kids, always watching if they were behind, playing with them... Then with age, he started coming to our house less and less. My DP of course visited him regularlly at his house and they are close. Understanding that young people have other interests, I made some efforts to invite them to eat or to organize family activities that everyone can enjoy like horse back riding, mountain biking, etc. Just like companies organize team-building activities, I thought that it would help, but it didn't. If there was no official invitation, SS didn't see the reason to visit.
At the same time, he's very involved with DP's other ex (ex Step mother who didn't even raise him) because her son is his age. Once at a Xmas gathering at ours, he initiated a long phone conversation with them, putting them on speakers and ending it with "I love you, family and I'm coming for a breakfast to your house tomorrow".
I think after that, he hasn't set foot in our house in about 1.5 years! Yep! He lives 35 min away and owns a car. The last 2 Xmases he conveniently had a light form of covid, but once that passed, he apparently didn't have a reason to come. Last year's DP's bday, he didn't feel like coming either. Father's day: never comes.
Finally he decided to visit my DP after his bday this year and my young son thought it was just some random guest! He know that he has a brother with that name and SD had to excitedly show him our family picture (taken when my son was a baby) to "proove" that it was his brother.
I was sad and I don't understand how nobody around me thinks it's a big deal.