Since I moved here to the US, my sister has come to visit me twice a year using the Visa Waiver Program
(no visa needed if stay is less than 3 months).

She has already come around 5 times in 3 years for about 10 days each time to see me. She has never had any problem in customs but I am concern about future trips. Since I live here, is it possible that one day they don't let her in cause they might think she wants to stay?

Last time I made her get a letter from her employer stating that she was on paid vacation and they were expecting her back in 10 days...
I am wondering if I am stressing this out or do our family members (lucky enough they can come to see us often) need to bring papers with them that prove they will return?

Thanks

It is always a good idea for a visitor to carry proof that they are indeed a visitor. The ultimate decision about who gets to enter the country and who gets turned away is made by the border authorities. Their assumption is that everyone who applies at the border for entry entertains the desire to immigrate to the US permanently - whether it is true or not. Your sister has not stayed for very long on her past visits and certainly hasn't abused her visa waiver which is definitely in her favour. Numerous visits, however, may trigger a more intensive scrutiny at any time. It would be unfortunate for her to have spent the money on a plane ticket and then be turned back because she was not able to convince a border guard that she is a bona fide visitor. Better to be prepared and not need the evidence, than to need the evidence and not have it.

My Parents have visited us 8 times in the last 2 years... their longest stay was 6 weeks. they have had no problems and they have never been asked for any sort of evidence that they are planning on returning back to the UK...

Kez

My Brother has been to the US that many times, not always to visit me.

Does not look like a pattern that would cause concern.

BTW Customs are not likely to be interested.

Thanks.

k1spain,

I agree with Boiler - your sister's pattern of visits is quite benign.

Should she start visiting for 3 months at a time with about 10 days back home between each visit her reception at immigration will change quickly, however.

Yodrak

I've been to the US 8 times in 15 months....never been questioned...

I know someone who lived in the US on the VWP or whatever it was before, never technically overstayed, worked as a contractor outside the US occasionally to make money for nearly 10 YEARS!