Who are the poskim that dealt with the shailo l'maseh of a father-in-law and possible chosson having the same name (mamash the same name, for exactly "Shmuel Yehuda" and "Shmuel Yehuda")
Answer:
The idea of being particular for same names comes from Rabbi Yehudah Ha-Chassid.
Some are particular for this matter, and others are not particular. From personal experience, I can say that in general Rav Elyashiv shlita was not very particular about this, whereas his son-is-law, Rav Chaim Kanievsky, is very particular.
For sources, see: Noda Biyhuda Tinyana EH 77; Ezras Kohen 5:7; Divrei Chaim EH 8; Orchos Rabbeinu 4:pp. 246-7; see also Maaseh Ish 7:130-1.