17 year age difference?

my fiance and I have a 17 year age difference. He is 40 and I am 23. We have been together for 2 years. I have not told my family his real age (I told them he is 35 instead of 40). We also told his family I am 26. I love my fiance very much and the reason we chose not to tell our families is because we dont want any unnecessary drama from either side. We have only had 2 family functions where the families are together and we try to avoid it as much as possible to make sure our ages dont slip. My question is, is it okay to lie to our families about our age as long as the two of us are okay with it?