I am really sorry for the incomplete info.
You say that, but you still haven't explained very much about the situation.
Have you heard the lateral thinking exercise about the man who lives on the 12th floor of an apartment block, and takes the elevator every morning, but every evening, takes the elevator to the 10th floor and takes the stairs for the last two floors, unless it was raining?
Trying to figure out the full story can be fun if there's a clever twist, and if you can ask questions and receive quick replies. It isn't so much fun when there's no twist, and each question requires a separate post and takes a day or two to be answered, so one's train of thought cannot flow properly.
That's how it feels with some problem descriptions, such as this one.
We are not mind-readers. We know a lot about electronics, but we don't know anything about your specific situation.
You need to imagine that we are strangers who are seeing your boards for the first time. You need to introduce the whole problem situation to us, starting from the beginning.
I'm going to ask you some more questions. These are all starting points. Don't just give simple minimal answers to them; use them as cues about the sort of information you haven't given us yet, and fill out the answers with useful information.
When I isolate the pin no.4 of 40106 from IC 555 then there is no heating in 40106. Only 555 getting hot.
Are you sure that the board is exactly the same as the partial schematic diagram you posted? Is it possible there is a layout error, or a track that goes off somewhere else that you haven't told us about?
Could it be faulty or damaged components? Have you replaced the 40106 and the 555 recently?
What does this board do?
What is it from?
Do you know who designed it?
How many of these boards do you have?
Why do you have more than one board?
When did the problem first occur?
Does the WHOLE board still work perfectly, even though the ICs are getting hot? (You said yes in your first post, but I ask again to be sure.)
Point from Steve that you didn't respond to: You are discharging the 10uF capacitor through the 555 without a current limiting resistor. You need a resistor between the cap and pin 7.
Question from Steve that you didn't answer: How hot are the chips getting? (Tell us how long you can hold your finger on them, for example.)
Question from Steve that you didn't answer: Can you measure the current draw from the 12 volt supply to the 40106 and to the 555 and tell us what they are? (Lift pin 8 out of the socket and put a multimeter on 200 milliamps range between the socket pin and the IC pin.)
Point from me that you didn't respond do: It's not good practice to drive a CMOS input negative; this will happen with the 10 uF / 100k arrangement that drives pin 3, when pin 2 goes low after previously being high. There are various fixes; a simple one would be to insert a resistor (e.g. 10k) between the junction of the capacitor and resistor, and pin 3 of the 40106.
Please imagine you're showing this board to someone who has never seen it before, and tell us everything about it that might be relevant.