Is it normal for a father to not know how old their own kids are

Me and my husband have been fighting a lot lately and IDK if this is worth a fight. I'm just annoyed. This morning my husband was drinking a beer. Our son asked if he could have a sip. He said yes. I said no. My husband said he had his first beer at 16. I said he's not 16. My husband asked our son how old he is. Our son said 14. My husband said "Oh shit. I was off." Like wtf. You should know how old your kids are. Especially your ONLY son.

Edit: No he's not an alcoholic. He doesn't really drink in general. The problems have been more situational. I lost my sister two months ago. Last month he lost his mom. Then we hit some financial issues. We are just in a rough spot.