Question: If two roommates share an apartment, must each one light Chanukah candles separately? Also, may a child be allowed to light Chanukah candles on behalf of the family?
Answer: If two people share an apartment but each one pays for his individual food expenses (and other expenses for that matter), they must each light Chanukah candles with a blessing and they do not fulfill their obligation with the lighting of one of them. Even if they are members of the same family, such as a father and son or a mother and daughter and the like, each one is obligated to light Chanukah candles on his own.
If, however, each one does not bear sole responsibility for his individual expenses, rather, they share mutual expenses for food and the like, they should chip in with one another for the cost of the oil and wicks or the candles and then only one of them should light with a blessing on the first night and the other should light and bless on the next.
Although a child who has not yet reached the age of Bar Mitzvah is exempt from lighting Chanukah candles and must therefore not be permitted to light the candles, for adults do not fulfill their obligation with his lighting, nevertheless, it is good to educate children (who have already reached the age of education) by allowing them to light the additional candles meant to beautify the Mitzvah every night. This means that one should light the first candle by himself (which is what is necessary to fulfill the minimal obligation of the Mitzvah) and allow the children to light the rest of the candles.
However, if the children are still too young to be included in the Mitzvah of educating them, one should not even allow them to light the additional candles meant for beautification of the Mitzvah; rather, one should only allow them to light the “Shamash” candle, for it has no innate holiness and is only meant to be used as an additional source of light.
Some are of the opinion that it is preferable not to allow even a child who has reached the age where he can be educated to light the additional candles meant as a beautification of the Mitzvah, for the lighting of a child does not constitute any Mitzvah and ultimately, the father has only lit one candle then. It seems that this is indeed the opinion of Hagaon Rabbeinu Yosef Haim.
Therefore, it is preferable to act in accordance with the custom of Maran Rabbeinu Ovadia Yosef zt”l which is that after lighting the first candle on his own, he would hold the hand of his son in his own hand and light the rest of the candles together with him. In this way, the father will have lit all of the candles in addition to having educated his son regarding the Mitzvah of lighting Chanukah candles.
Nevertheless, all this applies only to the Sephardic custom. However, according to the Ashkenazi custom, a child who has reached the age where he can be educated should be allowed to light his own Chanukah candles, for according to their custom, every member of the household lights Chanukah candles.