3. Being Motzi another person:

See Chapter 4 Halacha 2C and 5 for the full details of this subject!

Initially, one cannot be Yotzei an after blessing of Birchas Hanehnin [i.e. Borei Nefashos, Meiyn Gimel] from another, with exception to Birchas Hamazon with a Zimun, even if they are in a state of Kevius.[1] However, Bedieved, if one heard an after blessing from another, then if they were in a state of Kevius and both had intention to be Yotzei Motzi with the blessing, then it is valid. However, this only applies if the person was personally obligated in a Bracha Achrona. However, if he was not personally obligated in a Bracha Achrona then he may not recite an after blessing on behalf of a person who became obligated in an after blessing after eating a food or beverage, even if the other person does not know how to say the blessing themselves.[2] Likewise, if they are not Kavua together, one cannot be Yotzei the blessing with another.[3]

[1] Admur 213:2; Rashba 1:205; Ramban 196; See M”A 167:28; Admur 167:17

[2] See Admur 167:23; 197:6; 213:3; 273:6; Michaber 167:19; 213:2; Rosh Hashanah 29a; Encyclopedia Talmudit Erech Brachos Vol. 4 p. 344-350

[3] See Admur 167:15-17; 193:1-2; 213:1