Learn Farsi: فکر می‌کنم که پسرم به اندازه‌ی پدرش پرحرف است. - I think that my son is as talkative as his father.

The phrase به اندازه‌ی literally means 'to the measure of' or 'to the extent of'. In Farsi, to say 'A is as [adjective] as B', you use the pattern 'A به اندازه‌ی B [adjective] است'. In this sentence, it literally reads 'my son, to the measure of his father, talkative is'. Notice that the ی at the end of the phrase is the ezâfe linking it to the following noun, پدرش (his father).

How is the adjective پرحرف formed?

It translates to 'talkative', but it is literally made of پر (full) and حرف (word or talk). Combining پر with a noun is a very common way to create descriptive adjectives in Farsi, so a talkative person is 'full of words'.

Is the word که required after فکر می‌کنم?

که acts just like the word 'that' in 'I think that...'. Similar to English, it is perfectly fine to drop it in everyday speech, saying just فکر می‌کنم پسرم... (I think my son...). However, keeping it is standard in writing and slightly more careful speech.

Why do we use the suffixes م and ش on the family members here?