I've always wanted to have a big family, so when I met my DP who had 3 children (I had one), it was great. We didn't live together for 2 years, but did activities and I loved it. I've known them for 7 years now.
DP has 2 sons (now 18.5 and 21) from ex#1 and daughter (now 14) from ex#2. Ex#2 has a 21 year old son too, so SSs stayed friends with him and obviously that meant, with ex#2, their exSM. Normally, no problem with that. She gives the impression of a very warm person, made big efforts to be friends with ex#1 (but no efforts to have any relationship with me, her daughter's SM. As much as I find her affections towards others exagerratingly nice, as much as she treats me as an empty space).
So fast forward to now, I'm seeing that the situation with ex#2 and her non live-in boyfriend of 3 years is that they are considered "family" by SSs. I hear both exes and SSs visit each other. I have seen SS video calling with her and the boyfriend on separate occasions and the word "family" came up in conversation.
As for us, both SS stopped coming to our house at around 15 years old each. My DP is the one who goes to their house every week, so they see him and are close to him. I have a good relationship with them too. Over the last years, they probably visited us a few times per year, generally when I would invite them for dinner or organise activities that they and my son (13) could like, mountain biking, hourseback riding, etc. Sort of to create the sense of family. Obviously, we also visited them in their house. I have made other little efforts with them, like cakes for their birthdays, gifts, I try to talk to them (we do have some common interests, like investing), etc.
Finally, me and DP have a 3 year old son. They apparently love him. Obviously, I don't expect a great connection (although, some older siblings do want to be involved in younger sibling's life), but I did expect SOME efforts to stay close to us. Last time the 21 year old came to our house was 8 months ago! I heard that he was asking my SD (since he goes to her house) how big is our 3 year old and does he speak by now (!). The 18 year old came to our house a whooping 3 times this year (and it's almost amazing). The pandemic actually made things easier as fun activities for young people were closed, parties forbidden, studies were online, at some point, they didn't even work. How difficult is it to visit your father's family FFS? Take your computer and study in our house if you're so busy!
I don't know if the closeness of their exSM contributed to this (because people's time is limited), but somehow I doubt that an ex who was busy organizing her personal life after separation made the same efforts to cook and to organize activities for an ex's children as I did for my partner's children.
At this point, I want to disconnect and not be bothered by them at all. How do I stop caring after making all these efforts trying to create some sense of family and knowing that who they consider family is the woman who separated from their father 7 years ago?