Brother's paternal grandmother's only child/son: how is that person related to the speaker

The same question, asked 2 times: 18 Jul 2023 S4*, 25 Jul 2023 S4. Every wording below, oldest first.

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Question 1
18 Jul 2023 S4
5 $Priya pointed towards a man and said that he is her brother’s paternal grandmother’s only child. How is the man related to Priya?$
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Question 2
25 Jul 2023 S4
9 $Sonal’s brother’s paternal grandmother, named Seeta, is coming to Sonal’s party with her only son. How is Seeta’s son related to Sonal?$
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