As an extension to family relations, perhaps these words are useful:

step-mother (แม่เลี้ยง พ่อแต่งงานใหม่) / step-father (พ่อเลี้ยง)

half-brother (คนละพ่อ หรือแม่) / half-sister

mother-in-law (แม่ยาย) / father-in-law (พ่อตา)

brother-in-law (พี่/น้อง--เขย) / sister-in-law (พี่/น้อง--สะใภ้)

foster parent / foster mother / foster father (พ่อแม่ผู้เลี้ยงดู แต่ไม่ใช่ผู้ให้กำเหนิด)

god-mother / god-father (แม่/พ่อ ผู้ช่วยอุปถัมภ์ ในการเลี้ยงดู แต่ไม่ใช่ผู้ให้กำเหนิด)

cousin คัส ซึน / distant cousin ดิส ทั๊นทึ คัส ซึน (ญาติห่างๆ)

family friend (we make friends, don't we?)

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One more thing, a question like 'What does your father do (for a living)?' may be psychologically stressful to some children because  'Father may be dead or in prison or unemployed'. Perhaps, more neutral questions like: Does your father cook? Does your brother play soccer? What does your father usually cook? What does your brother play?

It is very important that teachers should avoid causing stress in children. Once stressed, they lose ability to learn; they may resent the teacher or the whole class; they may react violently; ... and so on. A little more effort in choosing class meterials and contents can create much happier learning environment for children and teachers ;-)