Is his spending on his wife who is also a relative regarded as kindness towards her family?

A husband’s spending on his wife may be obligatory or it may be charity and kindness. If his wife is also a relative such as the daughter of his maternal aunt, then his kindness towards her is also regarded as kindness towards her mother and to the husband’s mother too. 

The obligatory spending has to do with providing accommodation, food and clothing, as Allah says (interpretation of the meaning): 

“Lodge them (the divorced women) where you dwell, according to your means, and do not harm them so as to straiten them”

[al-Talaq 65:6] 

“but the father of the child shall bear the cost of the mother’s food and clothing on a reasonable basis”

[al-Baqarah 2:233] 

The Prophet (peace and blessings of Allah be upon him) said in his khutbah during the Farewell Pilgrimage: “Their (women’s) rights over you are that you should provide for them and clothe them in a reasonable manner.” 

A man will be rewarded for his spending on his wife, as al-Bukhari (1295) and Muslim (1628) narrated from Sa’d ibn Abi Waqqas that the Messenger of Allah (peace and blessings of Allah be upon him) said: “You will never spend anything seeking thereby the Countenance of Allah, but you will be rewarded for it, even (the morsel) that you put in your wife’s mouth.” 

Al-Nawawi (may Allah have mercy on him) said in Sharh Muslim: This shows that spending on one’s dependents brings reward, if he intends thereby to seek the Countenance of Allah. End quote. 

Al-Bukhari (55) and Muslim (1002) narrated from Abu Mas’ood al-Badri (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: “If a Muslim spends on his family, seeking reward for that with Allah, then it will be an act of charity on his part.” 

And Muslim (994) narrated from Thawban, the freed slave of the Messenger of Allah (peace and blessings of Allah be upon him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: “The best dinar that a man spends is a dinar that he spends on his family, and a dinar that a man spends on his mount (for jihad) for the sake of Allah, and a dinar that he spends on his companions (in jihad) for the sake of Allah.” 

Abu Qilabah said: He started with the family. And Abu Qilabah said: What man is greater in reward than a man who spends on young dependents and protects them from resorting to haram deeds – or Allah benefits them through him – and makes them independent of means. 

Whatever a man spends on his wife and dependents, he will have a reward for that with Allah, so long as he seeks reward for that, and intends to draw closer to Allah by doing what is required of him, or by making them happy, or by honouring his relatives and treating them kindly.  

And Allah knows best.