How to keep my kids safe and prevent them from getting hpv from my sister who lives with us?

Household contact ok: Thanks for the question, ron. You sound like a concerned parent. Since hpv is a sexually transmitted disease, it isn't spread by casual contact--being in the same room, using the same dishes, using the same facilities as your sister won't put them at risk. There is a vaccine available for girls and boys that offers protection against some strains of hpv. The cdc has more info about hpv at cdc.Gov.