if they are fruit flies it is easy to test and they are very easy to trap.
they are probably fruit flies
your brother should move all fruit to the fridge for now and keep the sink clean
- get some powdered yeast.
- get a small glass that has a narrow mouth
- put some powdered yeast in glass
- add a tiny amount of lukewarm water to yeast powder... mix to a paste like consistency using a spoon handle, use as much water as needed adding in small amounts... too much water.. then add more powder... you want a paste in the bottom of the glass
- get a sheet of paper, the stiffer the better (cardstock is best)
- make a cone lengthwise with the sheet of paper with the smallest hole possible at one end. the cone needs to be FAT at the top so that when you set it in the glass it won't touch the bottom. tape the cone together and "seal the seams" on the paper cone using tape.
- put the cone point down into glass... if it touches the yeast you havefailed, make a new cone
- if the hole on the end of the cone is too small adjust it using a sharp pencil, or such... it should be very small... just largeenough for the flies to enter
- seal the cone onto the rim of the glasswith tape... completely seal
trim the extrapamer from the cone... no reason for it to be too big... the smaller the cone lip above the glass the better
now you have the most effective fruit fly trap known to mankind
if the flies collect on the cone but don't enter your hole is too small
when your trap is full of flies fill it with water deprive the flies of oxygen by filling the glass with water (cone still attached).
dispose of trap and make a new one, or several and distribute around infested apt.