Over ex or not?

I've been talking to this guy for nearly three months now and two months before we started talking he got out of an 8 year relationship because his ex cheated , he did admit to liking me and his been putting in a lot of effort every single day and showing interest but I'm not sure if his ready to even move on being recently single and after such a long time, they literally still play mommy and daddy with their dogs and their friend groups are the same and what not, am I perhaps just a rebound or is it possible for somebody to get over someone so quickly after such a long time? Any advice would really be appreciated, thanks in advance
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4 mo
Would it be appropriate to bring this up or would it be out of line since we're not even yet dating?
Over ex or not?
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