Terumos 6:16

An offspring who is a servant does not impact a woman’s ability to eat terumah. For example, let’s say that a kohein’s daughter marries a Yisroel or a Yisroel’s daughter marries a kohein. That woman has a son who has a son with a woman who is a Canaanite servant. The son of that union is a servant. Now let’s say that the original woman’s son dies but her grandson, who is a servant, is still alive. If the grandmother is a Yisroel’s daughter who married a kohein, she may not eat terumah; if she is a kohein’s daughter who married a Yisroel, she may eat terumah. This is because her grandson is not halachically a descendant, since lineage doesn’t apply to servants.

Terumos 6:17

Let’s say that a Yisroel’s daughter marries a kohein, who dies. She had a child with her kohein husband, but she later marries a Yisroel. In such a case, she may not eat terumah. If her husband the Yisroel dies, but she had a child with him, she may not eat terumah because of that child. If that child dies, she may eat terumah because of her first child (from her kohein husband).