Can you connect RCA male to 3.5mm female?

EDIT: Firstly just reread your question which is pretty vague. Just incase don't try to plug an RCA plug into a 3.5 female. It won't work. Otherwise.....

You can successfully connect any 3.5mm audio source and any RCA audio source, be it mono or stereo/male or female. They pass thru the same signal type, its just a different plug. If you play electric guitar thats the same, thats a mono 6.5mm....

BUT, I think there's an easier option than you talk of. Get rid of the splitter (unless you need to connect multiple devices to the monitor).

Get an RCA to 3.5 cable, be it male or female (socket or plug) to suit the connections you need at both ends - source and monitor, or a combo of a cable and adaptor which is more likely etc. The cables and adaptors are readily available from any hi-fi shack type store and shouldn't cost more than $10-15. You won't need a high quality cable if you're running to monitor speakers.

FYI:

All audio cables like these work with a ground (or negative) being a '-', and a signal (positive) '+'.

A male RCA plug (as opposed to a female socket), when looking at it has a tip which is positive and the outer surround is the negative. For mono you will have one RCA, for stereo 2. You can connect a mono RCA to a stereo 3.5 and vice versa, it just won't be stereo but the same mono signal thru both the left and right speakers. A 3.5 (male) plug is a single plug containing both left and right channels. From the tip of the plug you will see 3 contacts, separated by thin plastic spacers. The tip is left, the middle right and at the base of the plug is ground, which is shared by both left and right.

You will have no problems what-so-ever with the right connecting cables/adapters. I solder these every day for work from raw cable and plugs.