I want to wish my ex and his mum Happy b/day. would it be awkward?

My ex's mums birthday is next week and then my exes is the week after. I want to wish her a happy birthday by sending a card(as maybe my ex too) but I'm afraid that it might be awkward because i haven't seen her in a while. I was with my ex for 1 year 2 months,(broke up around February). but 80% of that time I was with his family. I got to really appreciate & care for his family, especially his mum. They all were always extremely welcoming & I was very comfortable around them to the point it felt like my own family. But I haven't spoken to my ex since the 3rd of june. We're not exactly on bad terms, we broke up because feelings wasn't the same and at the time around the break up i was too hurt the first couple months to try & be friends like he asked and said he would. but i'm now fine and Overall the break was best and i guess things just didnt work & i won't lie I do miss him and his family as of the times spent together as of him with mine too, But I would just like to wish his mum a happy birthday, as we did get on as if it was my mum. But is that ok?

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