Reference for Yevamot 154:18

מה להצד השוה שבהן שכן יש בהן צד כרת

since he is forever ineligible to enter the congregation?<span class="x" onmousemove="('comment',' As he is subject to this restriction he is also subject to the other (cf. supra n. 1). ');">³⁴</span> — [The case of] forbidden relatives<span class="x" onmousemove="('comment',' Who are only forbidden to intermarry with each other, but are severally permitted to all the other members of the congregation. ');">³⁵</span>

Jastrow