germane

relevant and closely related to the point

Germane once carried a kinship idea. A germane point belongs to the argument like a close relative belongs in the family.

The story was funny, but it was not germane to the question the essay had to answer.

Germane is not about Germany in modern use. The helpful older image is kinship: something genuinely related, not merely nearby or interesting.

A germane example belongs in the argument. It has family resemblance to the point you are trying to prove.