Gerald Croft

rather attractive chap + well bred man-about-town

This suggests he is confident and comfortable in his masculinity. Also the reference to a “man-about-town” could hint to his later revealed unfaithfulness highlighting wrong, but accepted behaviour in 20th century Britain

the son in law i always wanted

This suggests that his wealth and social status makes him attractive in 20th century Britain

you can drink to me

This line is ironic given the fact that Gerald had already cheated on Sheila

we’d have done the same

This agreement with Mr Birling is used by Priestley to depict the wrong but accepted exploitation of the working class women in 20th century Britain

she was pretty-soft brown hair and big dark eyes

the fact he views her like this knowing a relationship won’t last suggests that he like many other men in 20th Britain see women as possessions.

we can keep it from him

Gerald undermines the true reality of how powerful socialism is, revealing capitalists as fools and blissfully ignorant of the true reality of the world