Indeed. the question is really up to what age.


That's right, it's quite common. So says the Pitchei Teshuvah to YD 242, the Aruch Hashulchan, Minhag Yisrael Torah OC 260, etc. They all say it's common and struggle to justify the practice. So the question is then, are they acting correctly or incorrectly?
You are also correct that squeezing into the bathtub can be a bit odd, and that's among the limudei zechut that the Acharonim cite as to why so many people are not makpid on this halachah sourced in shas and codified in halachah by the Rambam, the Rif, and the Rosh and the Rama, although very curiously pointedly ignored by the Tur and the Mechaber in both the Beith Yoseph and the Shulchan Aruch - that our baths today are not structured the same way as in talmudic times and therefore it's not as weird today, or that we don't sit in the shower today "beteilim" as they did in talmudic times...there are no shortage of limudei zechut.



That said, my rabbi once admonished me when I asked him why so many people read Mishpacha on Shabbat, the implication being that if so many people do it, it can't therefore be forbidden: He said, "Who cares what other people do. You know halachah and you have to do what's right".

So let's assume that the halachah that a son can't bathe with a father stands, and let's assume that those who ignore this halachah by going to the mikvah at the same time as their father or teacher or who shower at the same time at the gym after playing tennis have a limud zechut upon which to rely, but we aren't relying on any such limud zechut. In other words, the halachah stands at least of adult [above bar mitzvah] children. The question is then if a father bathing with a young child is acting contrary to halachah or not. Is there an exemption based on age?

The source for the halachah is a berayta in Pesachim 51a:

כדתניא עם הכל אדם רוחץ חוץ מאביו

Again, this is ignored by the Mechaber but the Rama codifies this le-halachah in two separate places.

YD 242:16:

לא ואם היה התלמיד במרחץ קודם לרבו, ובא רבו לשם, א"צ לצאת. (מהרי"ו בדינין). וכל זה לא מיירי אלא במקום שהולכים ערומי ערוה במרחץ, אבל במקום שהולכים במכנסים, מותר. (אגודה פ' מקום שנהגו) לב וכן המנהג פשוט ליכנס עם רבו ואביו וחמיו ובעל אמו ובעל אחותו למרחץ, אע"פ שבגמרא אסרו כולם, והכל הוא מטעם דעכשיו הולכים במכנסים

EH 23:6

עוד אסרו בגמרא לרחוץ עם אביו ואחיו ובעל אמו ובעל אחותו, ונהגו עכשיו היתר בדבר הואיל ומכסין ערותן בבית המרחץ ליכא למיחש להרהורא

So it's a slam dunk: You can't bathe with your father at least if you yourself are above bar mitzvah. All those very many people who go to mikvah at the same time are acting contrary to halachah, unless they hold by one of the many limudei zechut that the Acharonim offer. But ignoring the issue of adult children bathing with their fathers, what is the halachah regarding a child, a katan? Not so clear.

The halachah in Yoreh Deah is in hilchot kibbud av ve'eim - basically it's a breach of kibbud av to bathe with him and to see his ervah. However, that's not that big a deal because a father can be mochel on his kavod - if he wants to bathe at the same time for reasons of convenience or for any other reason, the father can be mochel on his kavod.

The other issue is the halachah in Even Haezer. Does it apply to a katan? Seemingly not. Siman 23 in EH is all about shichvat zera levatalah - and this has to do with what KR mentioned above. Also, Rashi on that berayta in Pesachim says the issue is hirhurim - that the child will see his father's ervah and will have hirhurim and will make the connection that he came from there ultimately. Does this apply to a six-year old? The rabbanim that I have spoken with in the past say no, this halachah of a child not bathing with a father does not necessarily apply to a six-year old. It is basically dependent on the maturity level of the child and at what age he starts thinking sexually and makes the sorts of connections that Rashi is speaking of [Note to Nooch: It's simply not true that children do not think of their parents as being sexual beings; this Rashi is evidence]. One rav suggested some time around ages 7, 8, or 9.

In other words, the issue of kibud av isn't really a problem if the father isn't makpid. And the other issue, of hirhurim, only applies to a child who will have hirhurim, namely a child older than 6 in most cases.

So can an adult bathe with his father? Seemingly not, but there are limudei zechut out there for those who are lenient and a great many people are indeed lenient in spite of the halachah codified by the Rama in two places.

And can a minor child bathe with his father? According to many poskim, yes, since it's not a violation of the halachah codified by the Rama since that halachah only starts to apply after a certain age. It's a matter of dispute what that age is and has to be determined on a case by case basis.

As I was shoveling my driveway this morning, my across the street neighbor came across the the street and handed me a book, Sefer Mora Horim U-chvodam Ha-shalem. The author, R. Naftali Shmuel Yonah, quotes R. Yoseph Shalom Elyashiv in a footnote that it's assur only from age 10, although "your mileage may vary" as they say on the Internet.

http://smg.photobucket.com/albums/v336/mel...bathing0001.jpg