Suggest Treatment For Infertility

my sister have a problem on how to get pregnant after more than 1 year of marriage, her husband is 60 yrs.old and she is 25..she got check up on her ob-gyne and take some medicines but still no effect on her, her husband has 4 children on the first wife and me already has 2 children, i cant see a reason why my sister not bearing a fetus on her womb until now..she's so desperate of having a baby..i hope you can help us..thank you!