Question

Inspite of having plenty wealth, he is unhappy ...is it grammatically correct?

Answer 1

I think no..... plenty of wealth.....

Answer 2

No
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it is grammatically incorrect

the correct sentence will be 
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Inspite of having plenty of wealth, he is unhappy

of is missing in the given sentence
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we can also write it as
1) despite having plenty of wealth, he is unhappy
2)Although he has plenty of wealth, he is unhappy