If your sister agrees to such an arrangement, that is between you and her. She, in essence becomes your payee, a conservator of your earnings. If you are happy with the arrangement, and she is happy with the arrangement, then it's all right. You might offer her a small percentage from your earnings as a thank you. It also wouldn't hurt to have the agreement in writing and for each of you to have a copy, as siblings sometimes have a change of heart. The written agreement would be something to show if you ever had to go to an arbitrator or court.
You may or may not do well on Hub Pages; there is no guarantee. Depending on your love of writing and how important you feel your messages have, you might consider writing without setting up the Pay Pal for awhile to get the experience and tell whether or not you are successfully getting traffic.
In the United States, our freedom of expression is regarded highly. So, I encourage you to write, if nothing else than for the experience. Hopefully, your country will be added to Pay Pal's listing in the future.
Blessings to you for every success!