I know someone who was living with and having a sexual relationship with an alien who was already married to someone in Mexico. To get citizenship for this immigrant, the person adopted the immigrant. Is this legal?

Edit:
I wasn't following what you said

I agree with Fr_Chuck but what is confusing me is if the adopted Mexican is married how old is he that this person adopted them?

It is not legal to have sex with your children, so if they adopt them, that is illegal.

Fr_Chuck maybe you can clear my confusion if the Mexican is married and then adopted then I wonder how old they are.
Is the adoption an 'adult' adoption so they can be a citizen or something?

I do agree that it has illegal or at least *immoral* written all over it.

i know someone who was living with and having a sexual relationship with an alien who was already married to someone in Mexico. To get citizenship for this immigrant, the person adopted the immigrant. Is this legal?

I don't have enough details to answer your question. Please give more details... how old is US citizen? How old is the alien? What do you mean by "adopt"? Etc.

To apply green card for adopted child can be done only when the child is younger than 16 years old and within this time frame, the child must be with adopted parent(s) for over 2 years.

Having sex with underage individual is illegal in every country. If you have evidences, call the cop.