Can my fiancée live with me and my two children if he is a registered sex offender in the state of Alabama? When we get married , will it make a difference ? I really need to know what the risk are because I can't lose my kids. Please anyone with any information on ALABAMA laws on this situation please help me out .

This is a global website. Not sure if very many people will know ALABAMA law.

It will, however, depend on his level of offense. Did he pee in public? Did he molest a child?

This is the Alabama law. It says if step child was a former victim. I can't find anything on future step children.
ALA CODE § 15-20-26 : Alabama Code - Section 15-20-26: ADULT CRIMINAL SEX OFFENDER - PROHIBITED RESIDENCE LOCATIONS, ETC (http://codes.lp.findlaw.com/alcode/15/20/2/15-20-26)
I'd call CPS and ask 'hypothetically'

As J_9suggests the type an level of offense will be an issue here. Also the ages and gender of the children.

For example, if your fiancée was convicted of statutory rape because at 18 he had consensual sex with his 15 yr old girlfriend, it might not be a problem especially if you have sons. But if he was convicted of abusing young boys, then yes you would likely lose your children.

The "victim" was 15 at the time . The charge is rape in the 2nd . Hope this helps !

And how old was he at the time? When someone is listed as a sex offender, they are usually assigned a level with the highest level being the most likely to repeat. Also, we when ask for more info, it helps us help you if you provide all we ask for. I asked for the ages and genders of your children.

Based on this:

The "victim" was 15 at the time

I'm guessing this was a statutory rape charge where he had consensual sex with someone under the age of consent. The law in Alabama is:
Section 13A-6-62
Rape in the second degree.
(a) A person commits the crime of rape in the second degree if:
(1) Being 16 years old or older, he or she engages in sexual intercourse with a member of the opposite sex less than 16 and more than 12 years old; provided, however, the actor is at least two years older than the member of the opposite sex.

So this could be the exact situation I outlined, he was 18 and had consensual sex with his 15 yr old girlfriend. Not very smart of him which brings into question being fiancée material. But not likely to repeat so not likely to cause you to lose your children.

But not likely to repeat so not likely to cause you to lose your children.

Ah, yes, there is always a caveat.

If the father(s) of the children know about the "fiancee's" sexual background, that could come into play in a custody hearing. If the father(s) have a stable home environment with no ties to illegal activity, the OP could possibly lose custody.

That's my guess too.

He can not even marry you without permission.

And he will need PO permission to live with you, married or now.