Yes, Gambling addiction has strained a lot of relationships through financial instabilities emotional turmoil, social isolation, and family problems. Gambling which was meant to be a popular kind of entertainment for many and was designed to provide a temporary escape from everyday life and also help one to be more observant mentally task your brain and it is also good for your mental brain. When it becomes an addiction it causes financial strain the strain can manifest in various ways including the loss of shared savings, debt accumulation, and financial secrecy which may lead to strained communication between partners. This communication breakdown can prevent couples, friends, and associates from working together.
I have really saw two couples who share betting code for each other, yes they literally bet the same matches and the day it went well, they celebrate together and the days it cut, they laughed it off and act as if nothing happened, that is what relationship is about right, mutual understanding and the fun of it and what amaze me about their betting spirit is that they don't fund each other, each one of them bet with their money and it's literally a penny from what they earn, so it's nothing to worry about and they discussed about the amount they stake each week to avoid unnecessary later explanations.
I don't think gambling affects relationship if you are been open to people around you, tell them you do and it doesn't change anything. Here, it's a normal thing as side husle for some and make sure that they have another means for putting food on the table, the day they won, they cheer up their friend and family and the day they lost, they still cheer up and turn up to other activities as if nothing really happened. Isn't that is how gambling is meant to look, fun fun all day.
It will start affecting your relationship if you are using money that is needed for your basic expenses.
From your example, you said they are just using penny from what they have earned. This is why, they have no problem.
But once people are abusing their funds and spending more than what they can afford, problems will arise.
Your relationship with family, friends or colleagues will be strained especially if you owe money from them due to your gambling habits.