Hadlakas Neiros Shabbos-Sharing candelabra and Chanukah menorah
It at times occurs that there are extra branches on the candelabra, or Menorah and there is another person lighting who does not have a candelabra/Menorah and hence would like to use the extra branches for his/her lighting. The question arises as whetehr it is valid for two people to light on the same Menorah or candelabra. This question applies both to Shabbos candles and Chanukah candles.
May two people light Shabbos candles on the same candelabra?
Two people are not to light Shabbos candles with a blessing on the same candelabra even if it contains many branches. [Some Poskim rule one may be lenient in a time of need.]
May two women share candelabras if they will also be lighting some Shabbos candles not on the candelabra?
If one is not lighting all of her candles on the candelabra then she may use an extra branch to light some of her candles.
May two people light Chanukah candles on the same Menorah?
 Admur 263/10; M”A 263/15; Shelah Shabbos Ner Mitzvah 132a
Other opinions: Some Poskim rule it is permitted for two women to light on the same candelabra. [Elya Raba 263/18 in name of his grandfather; brought in Beir Heiytiv 263/12 and Machatzis Hashekel ibid; Kaf Hachaim 263/53]
 P”M 263 A”A 15 and Kitzur SHU”A 75/10 allows one to be lenient in a time of need, based on the other Poskim brought above.
 Pashut, as in such a case there is no worry of a blessing in vain being that the blessing being recited is also going on the candles that are not on the candelabra, and hence the candle on the candelabra does not affect her Mitzvah in any way.
 Chayeh Adam 154/11; M”B 671/12; Kaf Hachaim 671/22
 M”A 671/2; M”B ibid