Yes, a family member can use your Oyster card, but only under specific conditions. If you have a standard "Pay As You Go" Oyster card with no personal discounts or railcards attached, it is fully transferable; you can lend it to a spouse, sibling, or friend as long as you aren't both trying to travel on it at the same time. However, if your Oyster card has a Travelcard (7-day, monthly, or annual) or a personal discount photocard (like a Zip 16+, Student, or 60+ photocard), it becomes strictly non-transferable. Transport for London (TfL) view using someone else's discounted or season pass as fare evasion. If a family member is caught using a card registered with your photo or personal discount, they can face a penalty fare of £80 (reduced to £40 if paid within 21 days) or even criminal prosecution for fraud. In 2026, it's safer for each person to use their own contactless bank card or mobile phone for "Pay As You Go" travel to avoid any accidental breaches of TfL byelaws.