All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
If this girl is religious and has good moral conduct, then there is no harm in you marrying her, and the difference of age between you and her is Islamically not a factor. For more benefit, please refer to Fatwa 89248.
Dear brother, you should be careful not to be superstitious about the death of her sisters because superstition and the belief in bad omens is prohibited. Rather, this is a kind of Shirk, as the Prophet, sallallaahu ‘alayhi wa sallam, said: “Believing in bad omens consists in Shirk.” [Ahmad, Abu Daawood and Ibn Maajah]
Allaah Knows best.