Assuming A and B are both from either Neptune or Jupiter (and not from a third planet) and both either Woman or Man (and no other gender)

There is, a priori, 16 combinations  : WNWN ; WNWJ ; WNMN ; WNMJ ; WJWN ; WJWJ ; WJMN ; WJMJ ; MNWN ; MNWJ ; MNMN ; MNMJ ; MJWN ; MJWJ ; MJMN ; MJMJ

The first sentence informs us that

They can't be both from Neptune and A being a man, because then the sentence would be true but said by a man from Neptune. This removes the MN.N combinations. Nor can one of them be from Jupiter while A being any combination that would make them truthful. This removes WN.J and MJ..

About the second sentence  :

This simply means that A and B have a different "thruthness" , so it only allows WNWJ  , WNMN  , WJWN  , WJMJ  , MNMJ  , MNWN  , MJMN  , MJWJ.

When we put that together  :

That leaves WNMN  , WJWN  , WJMJ  , MNMJ. If we are looking for a Man then our best bet is B since, in the only case where B isn't a Man (WJWN), A isn't either.

Assuming A and B are both from either Neptune or Jupiter (and not from a third planet) and both either Woman or Man (and no other gender)

There is, a priori, 16 combinations: WNWN; WNWJ; WNMN; WNMJ; WJWN; WJWJ; WJMN; WJMJ; MNWN; MNWJ; MNMN; MNMJ; MJWN; MJWJ; MJMN; MJMJ

The first sentence informs us that

They can't be both from Neptune and A being a man, because then the sentence would be true but said by a man from Neptune. This removes the MN.N combinations. Nor can one of them be from Jupiter while A being any combination that would make them truthful. This removes WN.J and MJ.

About the second sentence:

This simply means that A and B have a different "truthiness", so it only allows WNWJ, WNMN, WJWN, WJMJ, MNMJ, MNWN, MJMN, MJWJ.

When we put that together:

That leaves WNMN, WJWN, WJMJ, MNMJ. If we are looking for a Man then our best bet is B since, in the only case where B isn't a Man (WJWN), A isn't either.