It's said that "A man born in thiruvonam or shravana nakshatra will be blessed with a good wife". Is that true?

No nakshatra in and of itself can assure happiness from wife or anything else. 

FYI, there have been numerous men born under shravana star who have been killed by their wives. So don't walk around thinking ignorantly that you will be blessed with a devoted wife on account of your birth star.