Personal Space
There is often a need for spaces that are not part of the common area in that they're not be used by every family member, but that are also not part of the sleeping space. Examples of these include children's play area, office space for managing the household finances, a place of your own, and a home office.
Children's Place: This is for parents who wish to contain the majority of children's activities to a part of the house: sometimes that restriction is to limit them (or rather limit their toys) to a room or two, and other times it is just keeping children mostly out of your bedroom and home office. In this case, make it so those spaces are at least a little isolated from the ones the children will frequent. For example, make sure children's noise doesn't end up going directly into your bedroom.
Often children are given a specific play place--either a separate play room or as part of a larger bedroom. Wherever the play space, consider that many children don't like to feel isolated, so this will work best if space is fairly adjacent to the common area. If it isn't, don't expect the children to stay there. If their bedroom is to be their play space, consider locating it close enough to the common area
If the space is to be in the children's bedroom, there are various space saving ideas for making the children's bedroom into an effective play area. One is to put the beds could be in an alcove with toy storage underneath, leaving the rest of the room for play space. Another is to use a bunk-type, removing the lower bed and replacing it with a desk. The alternative is to make their bedroom as small as possible, and use the saved space for a separate play space.
Bill paying: Everyone gets bills, has a checkbook1, and there are often bank statements, retirement account statements, receipts for things, owners manuals, coupons, brochures for things you might want to do and so on. Some people keep little of this, or keep it digitially and others keep it all. For a young family with few accounts who doesn't save many records, a drawer in the kitchen or maybe in the living area works fine. If you're going to have a filing cabinet with records you need to figure out where that goes. One option is that records go in the attic (assuming you have one see storage), and the other is to build a space for it: a mini-office.
This mini office can go in an alcove off the common area or an alcove off a hallway, or even a corner of a guest bedroom, but beware of noise conflicts if there will be a phone or typing at a keyboard. If there is a quiet room ("away room") in the common area, the bill paying might be able to go there as well. It can be quite small, or if it has other uses, like a place to occasionally work at home, it might need to be a small room in its own right.
Home Office (work): if you work from home, you'll want a space that is disconnected from the rest of the house, and if clients come to that office, you'll need a separate entry. In order to function as a work space, your home office has to feel like work and not part of the home, otherwise many people--especially for those who are prone to procrastination--find themselves doing everything except the task they need to do.
In addition, if you plan on deducting that space as an expense, the space needs to primarily for work.2 If clients don't visit and attic office can work well, and if you do have clients, you may be able to add a door and an exterior stair. Although having a commute of only a few feet sounds great (and saves fuel!), many people find it not that practical, and don't like working in a vacuum.
Place of your own: placing this space is very personal, and depends on what you want out of it. In general these spaces are more private and quiet, and if that is the case, put it on your bubble diagram as such. Otherwise it can be a floating room, allowed to fit wherever the layout will easily accommodate it.
Notes
1. in these days of autopay there is much less use for a checkbook, but there are still bills that pretty much require you to pay by check.
2: IRS rules change periodically, check with the IRS for the exact rules.