I know how difficult it is to say no when someone asks for money, particularly when there are children involved, but you have to summon up the courage to say "no", maybe 'softening' it with something like "No, sorry, I don't have any spare money to lend you right now" if you'd rather not just say a flat out no.
A neighbour of ours (with one child) would come along roughly every 4 weeks, so a few days before getting their disability benefits, and ask to borrow money, generally for their pre-pay gas meter as they'd need hot water and heating. They would always pay it back on getting their benefits, but we always worried that this would leave them short for the following month. Sometimes we'd be scrabbling about for change to make £5.00 up to get them gas again as we don't often keep a lot of money in the house (to get lost down the side of the sofa), or we'd be waiting for pay day or tax credits day ourselves! We'd also give them milk and\or sugar etc. when needed (and not expect it back). We decided we couldn't always afford to lend them money so would have to start saying no.
One day they turned up with their laptop and asked us to help them download a particular app. We said yes, so they came in and we found out they wanted to use a particular gambling website. This didn't sit right with us as we don't gamble and don't want to lend money to people who choose to risk losing their money gambling when they don't have enough for milk\sugar\gas etc. without losing money betting. So it made it easier to not to lend them money anymore.
We also saw them using the local betting shop in town and our stance is - we won't lend money to people who know they are going to be short on money later in the month if they knowingly waste it on 'games of chance'. We also brought up the subject of gambling in conversation and they didn't deny they gambled. We were going to have to say no to lending more money as we are skint ourselves, but their gambling choice made it easier to say no.
The only time we have lent them money since was when we had the bad snow and the heating was on full blast so costing a lot more, no matter the financial circumstances we couldn't risk them not having heating for nearly a week in sub zero temperatures, we are not completely heartless. So, in a genuine emergency situation, we would still lend them money.
It is hard to say "no, I can't lend you anything", especially the first time (with the pleading eyes and knowing there are children involved in particular), but you will be stuck lending if you don't say no eventually.