I recently married a divorced woman with a five year old daughter. I have not and probably will not adopt her legally in the forseeable future because she has a father who is in the picture and would not agree. However my new wife and I are orthodox. i have several questions regarding yichud which have arisen in our marriage. 1. Am I permitted to hug and kiss my step daughter if she wants me to or give her a kiss good night? 2. What about placing my hands above her head for a bracha erev Shabbat as I do for my son and will do for our future child (G-d willing) soon.? 3.What other restrictions or considerations should there be in our home?
ב"ה Shalom Firstly, I wish you well in your marriage. May it be happy and everlasting. Rav Moshe Finestein zt"l was lenient in regard to yichud of stepchildren and in regard to kissing and hugging these children.( אגרות משה אבן העזר ח"ד סי' ס"ד However many contemporaries strongly opposed this opinion and had their reservations of his far reaching "heter". (שו"ת "שבט מיהודה" אבה"ע סי' כא), דבר יהוש" (ג אבה"ע תשובות טז-יז) האדמו"ר מליובאוויטש ב"אוצר הפוסקים" (ט עמ' 259, 263), ה"מנחת יצחק" (ט סי' קמ; ד סי' מט אות ט), ה"דברי יציב" (אבה"ע סי' מו),) I don't see myself as one worthy to decide in this issue and therefore I followed the responsa brought in Mareh Habazak, מראה הבזק חלק ו פט which was endorsed by many Gedolim in Eretz Yisrael, which saw the ruling of Rav moshe Finestine zt"l, as a basis when other mitigating circumstances are present. Consequently, since your step daughter is over 5 years old , the laws of yichud DO apply. So therefore, if your wife were to leave you alone with your stepdaughter for a short time, the door should be left open or even if the door is closed if the biological parent will be returning in a short time, it would be okay. For a long term period of remaining alone to avoid the issue of yichud, if the situation arises that you are required to be with your stepdaughter while your wife is out of the house, you can rely upon the presence of another boy over age five, or of another man during the day or the presence of two men at night. Alternatively you can rely upon the presence of 3 other girls above age 12, among them may be your own biological girls. As far as placing your hand on her head for a blessing, placing your hands over her head is fine as well. So though in theory, I have tried to answer your question, there are all sorts of situations which arise over the years of raising children and you may have the need to consult Rabbonim on all sorts of issues. Therefore, though I am happy to assist you on your initial question , I suggest follow the guidance of a local rabbi who knows you personally so he will be able to follow through as the child matures. All the best