Is it normal to still be friends with your in-laws after your sibling dies?

I lost my sister to cancer 6 and half years ago, and her husband and I have become good friends over those years. For one, I can't thank him enough for how much and how well he loved my sister especially in her final years. For another, we both are nerds, trekkies, outdoorsy people, so we get one another. He and my sister were married for 9 years (she was sick for 5 of those years). I'm also really close to her first husband - he came into our lives when I was 8, she was 15, they married when they were 18 and were together 15 years - so he's been in my life (and is the father of my oldest nieces) for more than half of my life. There is definitely NO romantic interest in either... but I'm curious if you think it's normal to still be such good friends with my in-laws? Is there a point where one should let go of those familial ties after a sibling has passed away? I ask because I've had people tell me I'm weird, but I don't think it's weird at all, and find it pretty natural, honestly.

Is it normal to still be friends with your in-laws after your sibling dies?
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