Hey pipo! Am in my 20's and I happen to be in love with my aunt.. Tho we not related bloodwise... We used to ignore each others feelins 4 about 2years but then we just decided to start datin undercover.. Am not ready to come out of the relationship because it means a lot to both of us... The question is,are we allowed to marry? Is it normal to fall in love with her?

Regardless of your feelings for each other you both need to be adults about this situation and end the relationship now.
Weither if she is related to you by blood or not does not matter the point of the matter is she is your family and it is not morally healthy for you two to be in this romantic relationship.
Think about how your family would feel about this and if you two were to ever have kids, it wouldn't be fair to them,

You are 20 and how old is your Aunt? You say she is your Aunt by marriage - does that mean she is still married? Are you allowed to marry? Legally, yes, you can get married, if she is free to be married, and you are living in a state that will marry you. From your id here, it appears you are also a female.

Is it normal? Ummmm... no. But life happens. Your family may have some real moral issues here and you know that, or else you would not be sneaking around. It is time to come out from under the covers and be honest with everyone and deal with what happens.

Anyone want to be at their next family reunion or christmas diner??

Family is always family, you may cheat and lie to friends, you may do your boss wrong, but you don't do family like this.
This was not a natural and right relationship to start with, end it.
Please get counseling, this is just not right, no matter what excuses you make.