I'm almost 10 weeks and DH and I are waiting until our next ultrasound (in 3 weeks) to start telling people. This is our first child together. 
 

SS is 12, will be 13 when our baby is born. He has a 5 yo brother from his BM and a 5 yo cousin (SILs daughter). When his mom and DHs sister were pregnant, he seemed to get very clingy with BM and with FIL which we thought was pretty normal considering he had been an only child for so long and on DH's side he had been the only grandkid.

DH is nervous about telling him, especially because we have a high-conflict BM and he's worried she might make inappropriate comments to or around SS. We live in a different state than SS and because of COVID, it's looking like DH is going to have to tell him over the phone. SIL told us last week that she is pregnant and DH said SS took it pretty well this time, was excited about having another cousin and didn't seem to be nervous or jealous at all. I'm thinking he's older and will probably be a little more confident this time around but we still want to make sure he doesn't feel excluded or like he's being replaced or anything. 
 

Any tips on how to tell him about it? We have a pretty good relationship, I would say more like aunt/nephew than mom/son which I think is more appropriate in this step situation, but I still don't want him to feel insecure or anything like that. Not sure if we should FaceTime him together or if DH should just give him a call on his own? Tell him we care about him and are excited about him being a big brother? Just bring it up casually and gauge his reaction and go from there? DH is not fast on his feet so honestly it would be better if he had a game plan so he doesn't get nervous and chocked up. I told him it's really up to him how he wants to do it but he seems so overwhelmed. Any ideas?