did I do the right thing?

my ex (we broke up last year after 6 years together) messaged me today after not speaking with me for about 3 months. he was informing me that he may have to give up the cats that he took in and I helped take care of while we were together because he's moving and isn't sure that he will be able to take them with him. the Humane Society he would be giving them to (this is a last resort obviously) is no kill so either way the fur babies would be taken care of. he also knows that I can't take them in because I already have a cat and she does not play well with other cats. Now here's the thing, I've been dating a new guy since January and he's wonderful. I felt the need to tell him that my ex contacted me and for what reason. his reaction was very nonchalant? He made it seem like he didn't care. I just want to make sure that I wasn't being ridiculous by telling him. I just felt like there's no reason to hide that and if an ex of his contacted him I would want to know. opinions? Comments? Did I do the right thing or did I go overboard trying to explain myself to him when I really had no need to?