Assalamu alykum waramatulah wabarakatuPlease there is a girl am willing to marry in sha Allah but we are all from the same extended family but with different Mother and Father is it allowed for me to marry her?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

If there is nothing that makes marrying this girl prohibited, then there is no harm if you marry her. Allah has clarified in His Book the women that are forbidden for marriage, either because of family lineage, breastfeeding, or relationship by marriage, and then Said after that (what means): {And lawful to you are [all others] beyond these.} [Quran 4:24]

If by your question you are referring to marriage amongst relatives, then marrying relatives is Islamically permissible; Allah Says (what means): {O Prophet, indeed We have made lawful to you your wives to whom you have given their due compensation and those your right hand possesses from what Allah has returned to you [of captives] and the daughters of your paternal uncles and the daughters of your paternal aunts and the daughters of your maternal uncles and the daughters of your maternal aunts who emigrated with you….} [Quran 33:50]

The Prophet married Zaynab bint Jahsh, who was the daughter of his paternal aunt, and he married his daughter Faatimah off to his cousin 'Ali ibn Abu Taalib .

The ancestors and Muslims from the past until now continued to marry their relatives, and many researchers stated that the issue of genetic diseases cannot be made a rule and that such diseases may occur and may not occur.

Allah knows best.