Generally, the problem is not big. I applied for a passport in high school. At that time, the signature font was naive, and the handwriting was very different from now. Going back and forth at home and abroad has never been questioned.

Your father's situation, as long as you pay a little attention when signing in the future, don't be different from your wife. In case of doubt, it can be explained that this is the previous handwriting, and now my hand is injured, so the handwriting is somewhat different and so on. . . As long as the passport is my own, it is generally no problem. You can rest assured.