I'm going to have to disagree on this; it can happen but is in no way guaranteed or even likely. I never caught any crap from having a GF 15 years my junior, and neither did she that I heard about. Her family really liked what I was about, liked that I was really good to her and her kids, and that I took good care of them. I'm still on good terms with them, and they tend to think she made a mistake by moving on.Meh. It would still be considered weird or a huge age gap. Less stigmatized than your situation.
For my part, my family never made comments about me robbing the cradle or her just wanting to be cared for. Everyone just saw two people who got along well and were happy for us.