Do you think my uncle "sucks up" to his brother in law?

I have noticed that my uncle acts different when his sister's husband is around (my aunt and my uncle through marriage). Both their names are Joseph and both go by Joe. My aunts husband Joe is very gruff and strict. My uncle Joe (through blood) is normally laid back and happy, but when he is around my aunt's Joe, he acts grumpy and quiet. Its like his personality changes so that my aunt's husband will approve of him. Do you think he is sucking up just because they have the same name? Do people change their personality around other people just so they will approve? Do you think he wants him to think all Joe's are stern and grumpy and not pushovers?