Hi,
As of my knowledge, the 2 years multiple family visit visa can use as follows,
Case 1:Â 2 Years Multiple Entry Family Visit Visa who spends all the years in KSA:
1.1 You get 90 days initially once you entered KSA.
1.2 You can extend online via 'Absheer'Â for another 90 days with the payment of SAR 100 without exit the kingdom.Â
1.3 For next renewal (completion of 90+90 days), you should exit the kingdom(before 180 days). You can go any country like Bahrain, Dubai or your home country. There is option in 'KingFahad causeway' to exit and make U-turn for entry to saudia. No need bahrain visa. You can travel by Air or by road but it mention(in arabic) in your visa ('Air' or 'Open'). Check before you proceed.
   1.3.1 : Air mean, the visit visa holder can exit via air only.
   1.3.2 : Open mean, the visit visa holder can exit either by road or air.
1.4 Once you entered K.S.A after 6 months, then you get another 90 days. The process repeat from 1.1 to 1.3 till the completion of 2 years visa. Â
1.5 It means, you should exit compulsory 4 times within 2 years duration. The 4th time will be in your home country to process the visit visa again.
Note: For each Exit-ReEntry visits you can extend online once. It mean, every 90 days of each visits, you can extend online for another 90 days.
Case 2: 2 Years Multiple Entry Family Visit Visa who can't spend more time in KSA:
2.1: For example, If one visits Saudia on 2 years Family visit visa(Refer 1.1), he/she can spend 2 months here and goes back to home country then he/she comes after 6 months/1 year/20 months, then he/she can get 90 days from the date of arrival. Refer 1.1 and 1.2. in this case.
2.2: For example, If one visits Saudia on 2 years Family visit visa(Refer 1.1), he/she can spend 2 months here and goes back to home country then he/she comes after 22 months then he/she can get 90 days from the date of arrival without further online renewal.
Case 3:Â 2Â Years Multiple Entry Family Visit Visa who frequently visit other country.
3.2: For example, If one visits Saudia on 2 years Family visit visa(Refer 1.1), he/she exit the KSA before 90 days to visits other country the he return after one week or 10 days or a month, he/she will get 90 days from the date of return/arrival.  Each visits can extend another 90 days once within 2 years period and should exit before180 days.Â
For online extend, SAR 100 has to pay
For Exit and Return, No need to pay and it automatically renew 90 days.
Note: The above based on my knowledge and the information passed to me. Practically, not tested.