Welcome to the board. If you can pick them up and pet them etc, you should be able to bring them into your home if you want to. Your already existing cat may get a little bent at first but most times, they will get used to one another. If you don't choose to bring them in, you can take them to a shelter (I highly recommend a no-kill cat shelter if you have one nearby). If wherever you are from gets as cold and brutal as it gets here in the winter, I would get them some shelter sooner rather than later.
Welcome to the board.
Welcome to Cats & Kittens....
I agree with Leslie and Cat - if you can handle the kittens, they would make fine pets.