This section concerns things that weave people's lives together. Many of them are medium or long-term aspects. Some can be short-term, but may have lasting results. These are often ways in which people express closeness with their family of choice, beyond their genetic relatives.
Letting someone drive your car. This involves trusting another person with an expensive piece of equipment that, for most folks, is vital to everyday function. There may also be insurance concerns. Usually this is reserved for family members or significant others. Occasionally, close friends may be allowed.
Sharing clothes, jewelry, other personal items. This is common between siblings or close female friends. Sometimes roommates do it too. Wearing someone else's shirt or bathrobe is typical in romantic relationships, so can suggest a similar level of intimacy even in the absence of sex.
Giving someone your password and/or asking them to post to your online account. Essentially you're trusting them to "be you" at least briefly, such as to post why you won't be online today if you are sick or your internet connection is down. A mistake here can wreck your online relationships or cost you an account. Most people reserve this level of trust for family members, lovers, or perhaps very close friends.
Sharing a bank account or other economic feature. Most often done in family, this can also involve professional partners or housemates. It requires a high level of trust with valuables, as a mistake can cause big long-term problems. But it's a good way to show reliance among family of choice or people who share a lot of activities and purchasing responsibilities.
Packing someone's bag(s) for a trip. This requires a detailed knowledge of the other person so you know the right things to put in it. Plus it involves handling someone's personal items. Getting there and finding something left out really sucks. Usually it's done by people who live together, in whatever arrangement.
Cleaning someone else's living space. This shows care and knowledge on the part of the cleaner, and trust on the part of the recipient. You have to know what NOT to throw away or move. It's typical of family members and roommates. Coworkers may clean each other's desk, office space, etc.
Living together. This is a big step, even if it's just for a little while. Housemates are in each other's pockets; it's hard to keep secrets. Family members and lovers often live together, but housemates who are family-of-choice form a category of their own. If you don't want a romantic partner, a permanent housemate is a good choice for someone to share your life with.
Raising a child together. While usually done by lovers who are the parents, this is sometimes done by other combinations of people. For instance, one parent might leave the other parent and connect (sexually or nonsexually) with a new partner. A woman might decide to have a child without involving the sire, but instead share childraising with housemates. Due to family tragedy, anyone might suddenly inherit a child from a relative. In any form, this is a long-term commitment to making a family that affects not just the adults but also the child(ren).