What I understand:
Eg For the group of the 6 Tanaka siblings with 1st names Ashanti, Bidatz, Mikoto, Smith, Wesson and Yellow, assuming you would call each as 1st name-san, you might refer to them as 'Ashanti-san tachi', which I understand either literally means 'Ashanti-san and the others' or nonsensically literally means 'plural of Ashanti-san' but really means Ashanti-san and the others'.
Either way I guess 'たち' here is like 'et al'. (I guess it's similar to the Philippine word 'sila', where you'd say 'sila Ashanti' even though 'sila' ordinarily means 'they'. But maybe a better analogy is the Mandarin 们. Idk.)
Question: Can you refer to the siblings by 2 of them, and if so then how would you do so? Perhaps Ashanti-san と Bidatz-san たち?