Platting
Dividing one parcel into more than one is a regulated process, and the requirements differ depending on where the land sits and how many pieces you are creating.
People use "splitting the property" to describe both, but they are not the same amount of work.
Dividing a parcel into a small number of lots, typically without creating new public streets or extending utilities. Lighter review, fewer requirements, shorter timeline. Still needs a licensed surveyor and still needs approval.
Creating multiple lots with new streets, utility extensions, drainage infrastructure and dedications. Preliminary plat, engineering review, construction, then final plat. Months rather than weeks, and engineering costs well beyond the survey.
Jurisdiction depends on where the land is. Inside Springfield city limits, the city. In another incorporated town, that town. In unincorporated Greene County, the county. Requirements, fees and timelines differ between them, and this is the first thing to establish because it determines everything else.
Karst is a platting issue here. The Greene County Design Standards set criteria for development on sites with sinkholes or other karst features, and the general rule is that construction in a sinkhole is avoided. Setbacks apply to buildings, parking and sanitary sewers. On a site with karst, the buildable area on your plat may be considerably smaller than the acreage suggests, and you want to know that before you buy rather than during review. See sinkholes and your property.
Splitting off a few acres for a family member feels informal and often gets treated that way. It should not be. An unrecorded or badly described split creates title problems that surface years later, usually when somebody tries to sell or borrow against it, and by then the people who understood the arrangement may not be around.
Get it surveyed, described properly and recorded. It is not expensive relative to the mess it prevents.
Send the address and how many pieces you are hoping to create.