This is neither encouraged neither discouraged rather this is permissible. Zainab, may Allah be pleased with her was the first cousin of the Prophet salla Allahu alaihi wa sallam.  Ali was the cousin of our Prophet and he married his daughter Fatimah may Allah be pleased with them.

Shaykh in Islam what is the ruling on marrying first cousins or relatives? Is it encouraged or discouraged? You see in our communities it is seen as being a bit “odd” and so people kind of look down on you if you do that. I don’t want to go against Islam as I know many early marriages were to cousins.