Two women breastfed each others older son. one woman has a daughter as second child, the second woman has a son as second child.
My question:
Is marriage possible between the guy (second child of the second woman) and the girl (second child of the first woman)? Both children were not breastfed by other woman.
Well if i understood you well woman A and woman B breastfed each others elder son. So this son's are both considered as son's of each of the women. But this doesn't apply for their brothers or sisters. And therefore neither the daughter of woman A nor the 2nd son of woman B are by any means considered as foster sisters and they are therefore foreigners to each other and could get married.
Ibn Qudamah (may own translation,take it with care!) said: The child who has been breastfed is a mahram for his Foster mother and Foster siblings. And the same situation applies for his children and children's children etc. but it doesn't apply to his siblings or his parents or aunts (both maternal and paternal - this also applies for aunts and uncles in the follwoing) and uncles. Also the foster mother could marry the father of her foster child or his brother or uncles. And her husband could also marry the mother of his wife's foster son, or his sister or aunts. And the children of the foster mother and her husband -who are not foster siblings to the child- could marry the siblings of the foster child. Imam Ahmad said: A man can marry the sisters of his foster sister as there is neither a lineage nor breastfeeding between them. The breastfeeding only occurred between his foster mother and his foster sister.
Here are two references in Arabic 1 & 2
And Allah knows best!
Your question is confusing, maybe how you worded it, that's why I thought it was a duplicate.
The marriage between the guy and the girl in the scenario that you mentioned is valid since none of them was breastfed by the other mother.
yes you can marry in your case but you cannot marry with your breastfed sister or brother.
