How do you know if the age gap between two people in love is too great?
The magic number is 21! If you are 21 or over then love is more important than age. Some younger people mature quickly and find their own age of friends rather dull. They often seek out older people who they can relate too. Nothing wrong with that. Believe it or not sex isn't the first thing on the list for good partners, but intellect. If you have a fantastic sex life, but later find this person does not meet your intellectual standards you will soon miss that.
The only thing a person has to watch out for is they are not looking for a parent figure. Sometimes this is confused with true love.
If you are 21 and the person you love is 31 or even 40 and you both love each other and enjoy each others company there is nothing wrong with that.
I am almost 4 years older than my husband and an aunt of mine married a man who was 15 years younger than her. I have been married 33 years and my aunt was married for 50 years. True love has no age barriers, but please, make it legal in your State! Marrying someone under-age is not a good idea.
If this person is female and is 50 or older then remember, children are out of the question. Even men usually don't want to start a family so late in life. If you truly love this person then go for it!
Good luck Marcy