Sample letter that parents and relatives can show to immigration officers while entering USA on a visitor visa or tourist visa, requesting a 6 month stay.
You can also download the MS-Word Format of this Letter for requesting 6 months stay.
[Date of entry into USA]
The Immigration Officer,
I live in USA at the address mentioned above. I am inviting my [parents/mother/father] to stay with me for a period of  months. Since my [parents/mother/father] is not fully conversant in English, I am writing on [their/her/his] behalf. The purpose of [their/her/his] visit is to spend time with us and also tour the country. I will be accompany [them/her/him] during [their/her/his] tour.
Since I work full-time, I can only show [them/her/him] around and take [them/her/him] to various places on weekends. A six months stay would thus allow [them/her/him] to not only do this, but to also spend some quality time with us. [They/She/He] already [have/has] a return ticket for [Month, Year] and I have obtained health insurance for [them/her/him] for a period of  months. Therefore, I request you to grant [them/her/him] a longer stay in USA and let [them/her/him] stay for 6 months in USA.