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hello,

could you tell me the phrases are correct?

1.my son's-in -law car
2. one hour and a half drive
or one and a half hours' drive
3. a passer's-by testimony
4. the twins' Susie and Nathalie toys

thanks
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1. no-- my son-in-law's
2. I would say 'an hour-and-a-half('s)' (with or without hyphens)
3. no -- a passerby's
4. can't be done-- change to the 'of' genitive: 'the toys of the twins, Susie and Nathalie'

You are confusing possessives with plurals, Yogi. It is 'two sons-in-law', 'two passersby'.
Comments  
I would say 'an hour-and-a-half('s)' (with or without hyphens)

RH: I've never ever heard anyone say,

"An hour hyphen and hyphen a hyphen half", Mr M.Emotion: wink